German Patent Application No. DE 101 37 292 A1 describes a driver assistance system in which ambient data and the vehicle motion are registered or estimated and referenced to each other, whereupon a steering assistance torque is generated or adapted in the steering system. This is realized by registering the course of the roadway and ascertaining an appropriate setpoint trajectory for the vehicle movement, which is compared with the actual path of the vehicle, whereupon an assisting steering torque is produced to correct the steering. In this way, the vehicle is able to follow the traffic lane even without intervention by the driver.
A method for adapting lane width in a lane keeping system is described in German Patent Application No. DE 10 2004 037 298 A1. In order to keep the vehicle in the traffic lane, first the course and the width of the traffic lane are ascertained through a video system carried in the vehicle, these values being used as the basis for calculating a setpoint trajectory that represents the ideal line. A deviation of the vehicle trajectory from the setpoint trajectory is permitted; when that deviation is exceeded, a driver-independent steering wheel torque is exerted on the steering wheel. If the magnitude of the deviation of the vehicle trajectory from the setpoint trajectory is below a threshold value, no intervention occurs; steering of the vehicle is left to the driver.